Electric-quadrupole transition-rate measurement of a highly charged ion in an electron-beam ion trap using pulsed laser excitation from a metastable state

We present the lifetime measurement of the (4d(3/2)(-1)5s)(J=2) state in Pd-like I7+, which predominantly decays to the (4d(10))(J=0) ground state by an electric-quadrupole transition modified by strong spin-orbit mixing. We measure this microsecond-order lifetime in an electron-beam ion trap using pulsed laser excitation from a metastable state which is continuously populated by electron collisions. The measured lifetime provides a new benchmark for relativistic atomic structure calculations with d-state electrons.